Mutants of Streptococcus mutans, and organism associated with human dental caries activity, and which are defective in their plaque forming ability but retaining their ability to produce extracellular polysaccharides will be analyzed in terms of the extracellular glycosyl transferases they synthesize. Available data indicate that wild type strains belonging to various serological groups produce different enzymes or sets of isoenzymes. By comparing the mutant enzymes with those produced by the wild type strains, it may be possible to find that a particular enzyme (s) is common to all serological groups and which would be anticipated to play a paramount role in the production of plaque and caries. For this purpose, hydroxylapatite chromatography, disk gel electrophoresis and isoelectric focusing techniques will be utilized to separate and identify the enzymes produced extracellularly in glucose broth by these microorganisms. Enzymatic activity will be assayed by measuring release of reducing sugars (Somogyi method) and glucose presence by the glucose oxidase method. In vitro complementation of plaque formation ability will be attempted by growing mutants in pairs or triplets in culture broth with suspended nichrome steel wires. This would allow for recognition of mutations belonging to different cistrons and is a preliminary step to study genetic control of the synthesis of glycosyl transferases.